Sometimes for my entertainment, I start single player games with funky settings and watch the AI fight itself. This time, I decided to start the game on the Big USA map. After setting it up, the first AIs to meet were in large income disparity. The AI seems to randomly employ multi-attack in an erratic manner, and in some cases in the couple of games before, only one or two of the four AIs would use it. The remaining ones would never use it.

I noticed that when the AI meets another, for a couple of turns they fight normally, but then quickly lock down into a slow trench warfare-like state. AIs with five times the income of the opponent stall hard and do little more than build armies on the border with the much weaker AI, taking one territory from it every few turns, and continuing to build obscene amounts of armies. An AI that was down to five territories for over 20 turns did not get eliminated by the AI that fixated itself on it until roughly turn 35 in the Big USA game. Here are some screenshots demonstrating the issue:

This is turn 48. The light blue AI was up in Washington State (furthest northwest state). You can see the remainder of the incredibly buildup that the brown AI did "trying" to eliminate it. Another odd AI behavior that can be noticed here is that the stronger AI of two that meet likes to create a tentacle that encircles the territories of the opponent. This is notable in this first screenshot.

By turn 71, the time of this screenshot, the brown AI was in full war mode with the red-orange AI. Yellow AI's encirclement of red-orange is more prominent in this screenshot relative to the previous one. Brown AI can also be seen attempting to encircle red-orange here. One real oddity with this is that both brown and yellow attempted to encircle each other, leading to the tentacle of their that extends northward. The obscene number of armies being deployed on borders is also even more notable by this turn.

On turn 145, no drastic border changes have occurred. Minimal amounts of progress on the borders the AIs have with each other has been made. This is peculiar, as in the span of 74 turns, it would be thought that the game would be mostly finished, with one AI doing cleanup on the last few territories, if not done already. The gargantuan buildup on the borders continues to stand out greatly, despite some slight migrations in position.

Anyway, this was the oddity I observed when running AI simulations. Perhaps this is a glitch, or something that needs to be sorted out.